Electrolyte



D86li 19 i936. H WATERMAN 2,()62543 ELECTROLYTE Filed Oct. 22, 1955 INVENTOR ATTORNEYS Patented Dec. I, 1936l UNITED STATES ELECTROLYTE Herbert Waterman, Wantagh, N. Y., assignor to Aerovox Corporation, Brooklyn, N. Y., a' corporation of New York 'Application October 22, 1935, Serial No. 46,070

9 claims.

My prevent invention relates to electrolytic l cells and while it has its preferred applicability l but conditioned to produce substantial. improvement inY the resulting product, which in the case of the preferred application to condensers, in-

sures substantial constancy of various electrical characteristics, including power factor, leakage l ,f and capacity, all of which maintain their optimum value throughout the life of the unit.

Another object is to provide an electrolyte agglomerate with the desired excess of solid ingredient, which yet presents no gritty structure but 2 is and remains at all times extremely smooth and soft to admit-of rapid incorporation into the absorbent separators of conventional condenser structures in the course of assembling them, as by a rolling operation, and which by virtueof its vsmoothness and softness remains in intimate contact with the electrode surfaces throughout the life of the condenser.

Another object is to provide a simple method, requiring simple apparatus for treating paste electrolytes of conventional character, with the result of imparting thereto the improved characteristics above noted.:

As conducive to a-clear understanding of the purpose of the invention, it is noted that commercial electrolytic condensers have been sub- `ject heretofore to more or less fortuitous variations in power factor, capacity and leakage in the course of use and especially under different conditions of use, yand such variations have occurred regardless whether or not the unit was hermetically sealed. Efforts have been made to obviate these variations, but these have either failed entirely or involved the use of electrolytes or ingredients thereof, vofl'prohibitive cost.

According to the present invention, these difculties have been obviated by the simple expedient of homogenizing conventional paste electrolyte. The homogenization may be performed in any suitable apparatus, as, for instance, a

conventional milk homogenizer, but it is preferred and found adequate 'for present purposes, simply to pass the electrolyte paste between a pair of heavy iron rollers, exerting a crushing pressure upon the crystals thereof, which resuits in a smooth soft creamy paste homogeneous to the naked eye and even to a fairly strong magnifying glass.

Electrolytic condensers, especially of the dry type made according to conventional practice, as for instance, according to the teachings of Ruben 5 Patent No. 1,710,073, when incorporating the homogeneous or comminuted paste of the present invention, in lieu of the same paste not so treated, show a surprising improvement in operation. In particular, the power factor of the'freshlymade 10 condenser is improved in the order of 50 per cent, the leakage in the order of 5 to r10 per cent, the capacity per unit of area in the order of 16 per cent and moreover whatever electrical characteristics are present in the newly made con- 15 denser appear to be substantially preserved without appreciable change, even after the lapse of years whetherl on the shelf or in use.

While the theory is merely tentative, it is believed that the reason for the unexpected im- 0 provement in performance, as a result of the simple homogenization, comminution or crushing operation, is the stabilization of the physical structure of the paste thus treated. Electrolyte paste of conventional type, the solid ingredient of which comprises crystals generally precipitated from supersaturated hot solution, aords opportunity for growth of relatively large crystals about the initial nuclei precipitated. These larger crystals continue to grow as time goes on, 30 the rate of growth decreasing as the temperature is,v reduced, but proceeding for months. This entails progressive change in the electrical characteristics of the condenser incorporating such electrolytes and more especially in the ca- 35 pacity and power factor thereof.

By the present invention, the homogenizing, comminution or crushing of the electrolyte paste after its crystals have reached fairly large size, reduces these crystals to minute size and since 40 the paste aggregate is now largely of small solid crystals kept moist by the liquid carrier, with no great excess of such carrier, the aggregate is relatively stable physically and there is no marked opportunity for the crystals to grow as they might 45 if the liquid carrier were in considerably greater volume relative to the volume of the crystals, Thus, the smooth creamy paste'of the present invention remains stable, does not develop appreciable further crystallization within the condens- 50 er, and the original electrical characteristics for which the condenser is designed are maintained substantially constant throughout the useful life of the unit.

The cletrolyte of the present invention, while 55 by an etching process. paste with its minute crystals is thus permitted advantageously used with anodes made of smooth plates or foils, has particular utility with foils, the

supercial area of which has beenincreased as The smooth electrolyte more effectively to enter the minute pits or depressions of etched foil, rendering the entire surface thereof eective from the standpoint of capacity, where the larger crystals of a coarser paste might bridge across such pits or depressions and prevent adequate contact by the liquid ingredient of the electrolyte, with consequent impairment of power factor and loss of effective capacity.

Where paste electrolyte is employed that has not been subjected to the mechanical comminuf tion, l'mogenization or crushing operation, it is difiicult to roll the condensers, for in rapidly stiffening and crystallizing, the paste becomes relatively hard and dimcult to apply. At best, the application of such a paste is uncertain.

By the treatment of the electrolyte as set forth, and the resultant smoothness'and softness of the aggregate, it is feasible to pass the gauze or paper interlay through the paste electrolyte to become impregnated therewithin the course of enrolling the gauze or paper with the foil.

In the single figure of the drawings, there is shown in purely diagrammaticl form, an installation for the preparation of the electrolyte and the incorporation thereof in the condenser.

The electrolyte paste is fed through the outlet nozzle I I of a hopper III to the roller press or mill made up of contacting rollers I2 and I3 whence the comminuted soft paste is fed along a chute I4 into a tank I5 thermostatically kept at a temperature preferably in the neighborhood of 180 degrees F. The, gauze, paper or other porous interlay I6 is fed from a roll I1 through the paste I8 in the tank I5, excess being removed by scrapers I8 and the interlay impregnated with the paste is passed on to form the condenser roll R by sandwiching between two layers of .foil ZIJ and 2| fed from corresponding rolls 22 and 2l respectively. Since a second interlay is needed in all structures of the type under consideration to prevent direct contact between the upper surface oi' foil 20 as shown in the drawing, and the lower surface of foil 2|, the roll for such interlay is shown at I1' and the material is fed through the electrolyte in nsy While the invention is not limited to the use of any particular composition of paste electrolyte or mode of Acompounding the same, it has specific utility with an electrolyte made up of polyhydric alcohol such as glycerin or ethylene glycol and alkali borate, ordinarily ammonium borate. The alkali borate, such as ammonium borate,.may be introduced as such, preferably as ammonium pentaborate or the equivalent proportions of boric acid and ammonium hydroxide might be used. The proportions are such as to include the excess of salt to produce the paste. be combined in any manner adequate to produce the paste, but preferably according to the teach,- ings of Georgiev Patent No. 1,815,768, by driving oi water until a definite predetermined boiling point has been attained, which boiling Point Will The ingredients may vary somewhat with the voltage of use. Where ethylene glycol is used as the polyhydric alcohol, in combination with the ammonium borate and boric acid, the, boiling point for a 500 volt condenser would be in the neighborhood of degrees C. or 266 degrees F.vwhich electrolyte is also suitable for lower voltages, although a boiling point somewhat lower, say 120 degrees C. or 250 degrees F. will result in a better power factor for lower 'voltage ranges in the order of 100 volts. In the illustrative example the specific proportions may be 20 parts by weight of glycol, 20 parts by weight of ammonium pentaborate, and 10 parts by weight of boric acid.

In practice, the electrolyte in the gauze or paper I6, rapidly cools to room temperature, after leaving the tank I5, without marked change in the crystalline structure thereafter. However, the mass of electrolyte remaining in the tank at degrees F. for prolonged periods, say for 24 hours, will show evidence of increase in the size of crystals. It is, therefore, desirable from time to time to pass the contents of the tank I5 through the rolling mill I2, I3 for again reducing the size oi' the crystals. i

It will thus be seen that there is herein described electrolyte and method for preparing the same, in which the several features of this invention are embodied, and which method in its action attains the various objects of the invention and is well suited to meet the requirements of practical use.

As many changes could be made in the above method, and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. The method oi' preparing a paste electrolyte of the type comprising crystals moist with liquid having salt dissolved therein and useful in electrolytic cells, which consists in mechanically comminuting the crystalline structure thereof to render the paste relatively smooth and to inhibit the regrowth of crystals.

2. The method of preparing an electrolyte for electrolytic cells, which consists in preparing a hot supersaturated solution of salts, permitting the material to crystallize and then mechanically comminuting the crystal structureA in the electrolyte to produce a relatively smooth and homogeneous product, in which regrowth of crystals is inhibited.

3; -The method oi.' preparing an electrolyte for electrolytic cells, which consists in admixing polyhydric alcohol and alkali borate in proportions to produce a paste comprising crystals moist with liquid having salt dissolved therein and subjecting the paste to a mechanical crushing action to comminute the crystals.

4."I'he method of preparing an electrolyte of ingredients including glycerin, ammonia and boric acid, with the salt in proportion in excess of what will combine with or dissolve in the liquid portion; which method consists in cooking the ingredients to produce a hot supersaturated solution of substantially predetermined boiling point, permitting the mass to cool and crystallize CII into an agglomerate and then substantially homogenizing the product.

5. The method of preparing an electrolyte of ingredients including polyhydric alcohol of the group comprising glycerin and ethylene glycol, ammonia and boric acid, with the saltin proportions in excess of what will combine with or dissolve in the liquid portion, which method consists in cooking the ingredients to produce a hot supersa-turated solution of substantially predetermined boiling point, permitting the mass to cool and crystallize into a paste and then subjecting the paste to a mechanical crushing action to comminute the crystals.

6. The method of preparing an electrolyte of ingredients including ethylene glycol, ammonia and boric acid, with the salt in proportions in excess of what will combine with or dissolve in the liquid portion, which method consists in cooking the ingredients to produce a hot supersaturated solution of substantially predetermined boiling point, permitting the mass to cool and crystallize into a paste and then feeding the l paste between rollers to crush or comminute the individual crystals.

7. An electrolyte for electrolytic cells made of ingredients including polyhydric alcohol, and ammonium borate, the physical structure of said electrolyte comprising a smooth mass made up of a multiplicity of minute crystals of one or more of the ingredients and a. liquid carrier substantially moistening said crystals and without free excess.

8. The method of treating an electrolyte agglomerate comprising crystals moist with liquid having salt dissolved therein and incorporating it into an electrolytic cell, which consists in subthen incorporating the thus impregnated interlay with the electrodes in a condenser structure, and preventing excessive growth of crystals in the supply of previously comminuted electrolyte by subjecting said electrolyte to further mechanical comminuting action. A

HERBERT WATERMAN. 

